Can I attach CD to the shortest link and have a double rocker mechanism instead of having to drive the free links with an oscillator?
No, because double rocker mechanism needs rotational input at the crank, which will ruin the required complex motion. There are two options to generate the required motion:
- Attach an oscillator to either link OC or QD
- Use an external crank-coupler attached to a regular motor (6 bar mechanism)
perpendicular of D1-D2 intersecting on perpendicular of D2-D3 = Q
perpendicular of C1-C2 intersecting on perpendicular of C2-C3 = O
No freedom in design due to high constraints
Adjusting coupler design gives more options for the locations of the hinges
- Use the previous idea of coupler design to design a special coupler that has (1) AB attached on it and (2) has two points (OO and QQ) whose center of rotation are O for one point and Q for another point , such that when OO-QQ rotates about O and Q, AB goes to its three positions
- To identify OO and QQ on this special coupler, invert the mechanism: fix A1B1 and consider the rotation of OQ to go through the required 3 positions of AB; this gives 3 locations for each of O and Q which allows you to get the two centers of rotation (OO and QQ)
- This allows you to get more freedom with hingesβ positions (satisfy the requirement of a predefined ground)
01:11:44 Solved Example on Synthesis of four-bar mechanism